Electrostatic toner composition to enhance copy quality by improved fusing and method of manufacturing same

ABSTRACT

An electrostatic developer is provided that contains toner-containing image-forming particles and an uncrosslinked, linear hydrocarbon based homopolymer wax component, wherein the wax has a total number of branches in each of one or more chains that is less than 0.5%, relative to total number of carbons in said wax; wherein the wax is further characterized by having a set of endotherms as determined by differential scanning calorimetry (DSC) run at a maximum rate of 10° C. per minute, these endotherms being characterized by a primary endotherm and at least a secondary endotherm, the primary endotherm exhibiting a temperature range of between 70° C. and 90° C., and the secondary endotherm exhibiting a temperature range of between 95° C. and 110° C., and wherein the wax has a crystallinity of from 75% to 90% as determined by small angle X-ray diffraction analysis.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a developer for developingelectrostatic latent images in electrophotography, electrostaticrecording and electrostatic printing. More specifically, the presentinvention is directed to a composition and method that provides adeveloper which comprises toner particles and a wax to ensure thereduction and potential elimination of image offsetting by providingproper fixing or fusing during the electrophotographic process andmaintaining a stable, high quality image, during extended use.

2. Description of the Background

Visible image forming methods associated with toners usingelectrophotographic systems have been extensively studied and arecurrently widely used. Typical examples of these techniques aredual-component developing methods, which use image-forming particles andoften larger carrier particles, and mono-component developing methods,which use a toner comprising only magnetic or non-magnetic image-formingparticles. Details of such developing methods are described inKirk-Othmer, Encyclopedia of Chemical Technology, 4^(th) ed., 9:261-275(1994).

An image forming apparatus utilizing an electrophotographic method withtoner is well known. In the image forming apparatus utilizing theelectrophotographic method, images are generally formed onto a sheet ofcopy paper through the following processes.

After uniformly charging a photoconductor that serves as animage-holding body, images are exposed onto the surface of the chargedphotoconductor. Attenuating electrostatic charges during the exposure oflight forms a latent image. Then the electrostatic latent images arevisualized by developing with toner to form a toner image. The tonerimages are transferred onto the aforementioned medium and thereafterfixed on it by heating, pressure or solvent vapor.

In recent years, accompanying the rapid growth of computer technology,digital copiers and printers have been developed and become widely used.In these machines, mono-component developing methods have been appliedmore often to reduce the number of supply parts and ease of customermaintenance requirements compared with that of the dual componentmethod.

In the mono-component systems, toner is generally required to have goodfluidity and uniform chargeability in order to form a good qualityvisible image as described in U.S. Pat. No. 5,802,284 incorporatedherein by reference. The use of silica powder additives for tonerparticles to impart fluidity and chargeability properties has beenwidely studied and is one conventionally accepted method. Many US andinternational patents exist and are known that include the use of silicaor silicon dioxide with toner of various compositions. A subset of thesepatents relates to surface treatments of silica or silicon dioxide forspecific purposes to somehow enhance image quality characteristicsrelating to electrophotography. Examples of the use of hydrophobicsilica particles for toner includes JP 46-5782 A, JP 48-47345A, and JP48-47346A.

U.S. Pat. Nos. 5,464,722, 5,447,815, 4,868,084 5,702,858, 5,561,019,4,902,570, 4,618,556, 5,695,902, and 6,004,711 all disclose themanufacture of toners using a form of silicone oils, varnishes, silicondioxide particles or hydrophobic silica fine powder as some with surfacetreatments used as additives to enhance toner images.

The most common toner image fixing system for office and personal useprinters and copiers uses a heat fixing method in which a heated devicecontacts a toner image on the substrate under an applied pressure.Offsetting in such a system often describes the soiling or impropermarking on the imaged substrate by the toner. Cold offsetting is theterm usually used to describe the soiling that occurs when thetemperature of the fixing device is lower than the suitable toner fixingtemperature range. In this case, insufficiently melted toner adheres tothe surface of the fixing device and is subsequently depositedincorrectly onto the substrate. In contrast, when the fixing devicetemperature is higher than the suitable fixing range, the overly meltedtoner can adhere incompletely to the substrate due to a loss ofelasticity resulting in adherence of toner to the fixing device. Thesubsequent soiling of the substrate is usually termed hot offsetting.Actual offsetting is a complex phenomenon and frequently related to manyfactors including surface properties of the substrate and the fixingdevice material, chemical and physical properties of the toner, andtoner particle size.

One method which has been found to reduce or eliminate offsettingincludes the use of wax additives that have low softening temperaturesso the resultant electrostatically transferred toner images are fixedwithout smearing, improper spacing between lines and/or characters ormargin offset.

In a recent JP filing, JP 10-73952, a color toner formulation with a waxwith a number average molecular weight (Mn) between 1500 and 7000 isclaimed to provide better results regarding fusing characteristics.Normally, lower number average molecular weight (Mn) waxes have beenassociated with a phenomenon known as “bleeding”. In addition, thisKokai patent claims that the ratio of branched carbons to the totalcarbons in the wax is between 0.5 and 20.

Sakashita, U.S. Pat. No. 5,051,331, discloses a toner comprising abinding resin and a low molecular weight olefin copolymer. Sakashitateaches the low-molecular weight olefin copolymer has at least twoolefin monomer repeating units and has two or more peaks of melting attemperatures between 90 C and 170 C.

Tanikawa et al. U.S. Pat. No. 5,364,722, disclose a toner comprising abinder resin and a hydrocarbon wax, and heat-fixing methods using thetoner. Tanikawa et al. teach that the binder resin may be composed ofhomopolymers of styrene and derivatives thereof, and styrene copolymers,such as styrene-acrylate copolymer. Tanikawa et al. further teach thehydrocarbon wax provides a differential scanning calorimeter curveshowing an onset temperature of heat of absorption in the range of 50 to100 C, and at least one heat absorption peak in the range of 70-130 C.

Hagiwara et al., U.S. Pat. No. 5,389,484, disclose a toner having abinding resin having an acid component with an acid value of from 0.5 mgKOH/g to 100 mg KOH/g, a colorant, and defined aromatic amines. Hagiwaraet al. teach that the acid component of the resin interacts with theamino group of the aromatic compounds to form an amide bond therebycross-linking the polymer chains. Hagiwara et al. further teach thatthis can impart a rubber elasticity to the toner, so that itsanti-offset properties can be improved.

Suzuki et al., U.S. Pat. No. 5,538,828, disclose a toner resincomposition comprising a binder primarily composed of vinyl copolymerand an ethylene copolymer. Suzuki et al. further teach the ethylenecopolymer is prepared by copolymerizing ethylene and at least one alpha-or beta-derivative of acrylic acid or an unsaturated dicarbonic acidderivative. Suzuki et. al. further teach toner-separating agents such asa low molecular weight polyester or polypropylene wax may be added.

Taguchi et al., U.S. Pat. No. 5,466,555, disclose a releasingcomposition for a toner comprising a low molecular weight polypropyleneand at least one modified polyolefin. Taguchi et al. teach that suitablepolypropylenes include polypropylene homopolymers, and copolymers ofpolypropylene with one or more other monomers copolymerizable therewith,for example, ethylenes and olefins. The releasing composition may beused in toner which comprises the releasing agent, colorant, and binderresin. Taguchi et al. teach suitable binder resins include styrenicand/or acrylic resins.

Sawai et al., U.S. Pat. No. 5,565,294, disclose a toner containing acolorant, a binding resin, and a polyethylene having a melt viscosity of22000 to 26800 mPa-s at 140 C. Sawai et al. teach that when the meltviscosity of the polyethylene is less than 2200 mPa-s at 140 C, tonercomponents are not evenly dispersed in the kneading step in theproduction process of toner.

Inoue et al., U.S. Pat. No. 5,658,999, disclose production of propylenewaxes by polymerizing propylene with a solid catalyst formed of atransition metal compound or a reaction product between the transitionmetal compound and an organometallic compound, an aluminoxane and a fineparticulate carrier. Inoue et al. further discloses a toner compositioncomposed essentially of a binder resin, a colorant, and as a releasingagent, a propylene wax.

Akimoto et al. U.S. Pat. No. 5,707,772, disclose a toner comprised of aresin, a colorant, and a releasing agent. Akimoto et. al. teach thereleasing agent is a low molecular weight polyolefin polymer synthesizedusing a metallocene catalyst. Akimoto et al. further teach the numberaverage molecular weight of the polyolefin is from 2000 to 10000, andthe ratio of weight average molecular weight to number average molecularweight (Mw/Mn) is 1.6 to 3.5.

Osterhoudt et al., U.S. Pat. No. 5,811,214, disclose a developercomprising negatively charged toner particles comprising a polymericbinder, magnetic material, and a charge control agent wherein the tonerparticle surface contains particles of cerium dioxide,dimethyldichlorosilane treated silica, and dimethylsiloxane treatedsilica. Osterhoudt et al. teach the polymeric binder may comprisestyrene and an acrylate and/or methacrylate. Osterhoudt et al. furtherteach that useful additives include release agents such as waxes,including copolymers of ethylene and propylene having a molecular weightof 1000 to 5000 g/mole.

Eguchi et al. U.S. Pat. No. 5,928,825, disclose a toner comprising abinder resin, a colorant, and a lubricant. Eguchi et al. teach thelubricant comprises a modified polyethylene wax obtained by grafting amonomer selected from the group consisting of styrene and unsaturatedcarboxylic acid onto an ethylene homo- or copolymer.

Hashimoto et al., U.S. Pat. No. 5,948,584, disclose a toner comprisingtoner particles containing at least a binder resin, a colorant and awax. Hashimoto et al. teach that the binder resin comprises a hybridcomponent comprising a vinyl polymer component and a unit of polyestercomponent bonded to each other.

Kuwashima et al., U.S. Pat. No. 5,952,138, disclose a magnetic developercomprising a magnetic toner containing at least a binder resin, amagnetic material, and a hydrocarbon wax which is synthesized byreaction of carbon monoxide with hydrogen or by polymerizing ethyleneand which has a number average molecular weight of from 600 to 1000.Kuwashima et al., teach the wax should have an acid value of less than2.0 mg KOH/g, and that if the acid value is higher than 2.0 mg KOH/g,the wax's interfacial adhesion to the binder resin may become so largethat smearing of characters results.

Urashima, et al., U.S. Pat. No. 5,955,233, disclose a toner comprising apolymer obtained by suspension polymerization in an aqueous medium of apolymerizable monomer composition, a coloring agent, and optionally, amagnetic powder in the presence of an epoxy resin and a crystalline(meth) acrylic ester type polymer. Urashima et al. further teach anoffset-preventing agent may be incorporated, and that suitableoffset-preventing agent may include polyolefin wax which has a weightaverage molecular weight in the approximate range of 1000 to 4500,preferably 2000 to 6000, such as homopolymers of polyethylene,polypropylene and polybutylene, or olefin copolymers such asethylene-propylene copolymer.

Livengood, et. al. U.S. Pat. No. 6,331,372, disclose a tonerparticulates including a wax comprising an ethylene polypropylenecopolymer with a non-crosslinked copolymer other than the wax alsocomprising an ethylene propylene copolymer. The U.S. Pat. No. 5,707,771and related U.S. Pat. No. 5,955,234 disclose a toner for developing anelectrostatic image comprised of a binder resin, a colorant and a waxwhere the toner has specific rheological characteristics based onelastic storage modulus at specific frequencies where the toner shows agood fixability even at a high colorant content and shows an improvedfixability during fusing that occurs immediately after power is suppliedto a fixing device in a cold environment. The binder resin maypreferably include a low-modulus component and a high-modulus component.The waxes may preferably include both a high-melting point wax componentand a low melting point wax component.

U.S. Pat. No. 5,635,325 discloses a toner for developing electrostaticimages that includes at least a binder resin, a colorant and an esterwax. The ester wax is contained in 3-40 wt. parts per 100 wt. parts ofthe binder resin. The ester wax includes ester compounds represented bya formula of;R₁—COO—R₂wherein R₁ and R₂ independently denote a hydrocarbon group of 15-45carbon atoms. The ester wax contains 50-95 wt. % thereof of estercompounds having an identical number of total carbon atoms. The toner isespecially characterized by low-temperature fixability, wide non-offsettemperature range, good color mixing characteristics and transparency.

U.S. Pat. No. 5,741,617 describes a toner for developing electrostaticimages, which comprises a binder resin, a colorant and a waxcomposition, characterized in that the wax composition has a molecularweight distribution as measured by GPC containing an ester wax with aweight average molecular weight (Mw) of from 350 to 4000 and a numberaverage molecular weight of from 200 to 4000.

U.S. Pat. No. 5,747,213 details a method of forming a color toner imagewhere the color toner contains at least a binder resin, a colorant andwax, the wax having a molecular weight distribution measured by GPC.

Finally, U.S. Pat. No. 5,840,457 summarizes many of the solid toner waxproperties found to be useful for toner resin with magnetic black tonerparticles that are used to help control the degree of gloss, leavelittle residual toner, provide a high transfer efficiency, cause littleabrasion of the OPC and other cartridge components, and results in lessimage defects due to soiling of the members pressed against the bearingmember. Several wax characteristics are summarized in U.S. Pat. No.5,840,457 and it is indicated in this patent that low-molecular weighthydrocarbon waxes, as well as polyethylene waxes and long-chain alkylalcohol waxes are best suited to providing efficient transfer and goodgloss and with the waxes that possess physical characteristicscomprising a Mw/Mn=1.0-2.0 and a DSC heat absorption main peak between60 and 120 C.

Many references exist regarding toner compositions including waxcombinations to enhance fusing performance. The use of the propercombination for each specific composition is, however, unique andcomplex and therefore the need for proper wax agents in current specificformulations still exists.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an electrostaticdeveloper composition and method of using such a composition whereintoner performance is controlled such that the toner is suitable for thespecific development system, and is capable of stable high image qualityas determined by image density, background, resolution and other generalrequirements during long term use.

Another object of the present invention is to provide a toner thatreduces or eliminates the phenomena known as offsetting, smearing, orother print imperfections. Use of a specific wax has been shown toreduce the build-up of toner onto the fixing devices. There areessentially three basic features of the present invention that areunique: first, development of a toner composition with better fusingproperties as measured by tape peeling and rubbing that characterizesthe prevention of smudging or fusing as a result of the fusing rollerand/or fusing belt apparatus remaining free from contamination or tonerbuildup; second, the prevention of this toner buildup also helps reducebuild-up around the picker-finger; third, the wax of the presentinvention also reduces friction between the paper and the picker-fingerallowing for easier release of the picker-finger from the paper reducingthe propensity for scratches. In all three cases the use of the wax inthe toner composition of the present invention leads to better imagequality including higher image density (ID), lower background (BG), etc.

In addition, the toner allows for a wider temperature operating range ofthe fixing device without offsetting.

Another object of the present invention is to provide a toner which iscapable of stable long-term performance without any undesired tonercontamination of the electrophotographic system including thephotoconductor, the direct photoconductor charging apparatus, the fusingroller or fixing system.

These and other objects of the present invention have been satisfied bythe discovery of an electrostatic developer comprising toner-containingimage-forming particles and an uncrosslinked, linear hydrocarbon basedhomopolymer wax, wherein said wax has a total number of branches in eachof one or more chains that is less than 0.5%, relative to a total numberof carbons in said wax, wherein said wax is further characterized byhaving a set of endotherms as determined by differential scanningcalorimetry (DSC) run at a maximum rate of 10° C. per minute, saidendotherms characterized by a primary endotherm and at least a secondaryendotherm, said primary endotherm exhibiting a temperature range ofbetween 70° C. and 90° C. and said secondary endotherm exhibiting atemperature range of between 95° C. and 110° C.;

and

wherein said wax has a crystallinity of from 75% to 90% as determined bysmall angle X-ray diffraction analysis.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 provides a sample DSC (differential scanning calorimetry) scan ofa most preferred wax used in the toner of the present invention.

FIG. 2 provides a GPC (gel permeation chromatography) plot comparing amost preferred wax used in the toner of the present invention with PE130.

DETAILED DESCRIPTION OF THE INVENTION

The toner components of the present invention comprises a mixture of (1)toner components containing image-forming particles, (2) a low softeningtemperature, nearly linear hydrocarbon based homopolymer wax with aspecific molecular weight and crystallinity.

The above combination of components allows for high image density andclear images without offsetting formed during the electrophotographyprocess. The development of this process is at high-resolution power andindicates improved electrostatic recording is obtainable.

In electrophotography, electrostatic recording, or the like, in whichthe developing method and the toner according to the present inventionare used, the image-forming particles do not transfer to the non-imagearea and proper, non-offset images can be formed, thereby providinggreat industrial merit.

In the present invention, it is shown that a specific number averagemolecular weight wax with little or no branching, provides for betterfusing. In addition, and in contrast to conventional systems, it isshown that image density (ID) can be maintained using this specific wax,whereas conventional waxes with specific molecular weights sometimesresult in toner compositions that also result in lower ID's. Finally, ithas also been shown by further analysis, that the wax of the presentinvention would include less than 0.5% branching based on the totalnumber of carbon atoms in the wax molecule.

Here the branching or branch carbons preferably include those carbonscontained in the main chain.

It is desirable that the toner not accumulate excessively on the fuserroller, for excessive accumulation can result in mechanical failure ofthe fuser. The inventors have found that toner particles comprising alow softening temperature non-crosslinked linear hydrocarbon basedhomopolymer wax with a specific molecular weight and crystallinityprovides very good print quality without accumulating on the fuserroller to a degree which is likely to cause mechanical failure.Moreover, this special wax additive reduces or eliminates the phenomenonknown as offsetting and provides for proper fusing of the tonerparticles.

Toner particles in accordance with the present invention comprise aresin, a wax comprising a low softening temperature non-crosslinkedlinear hydrocarbon based homopolymer with a specific molecular weightand crystallinity, and optionally ingredients such as magneticcomponents, colorants and charge control agent.

Another embodiment of the invention includes an electrostatic developerwhich comprises a toner containing image-forming particles and anuncrosslinked, linear hydrocarbon based homopolymer wax component,wherein said wax has the total number of branching carbon atoms presentin each of one or more chain branches that is less than 0.5%, relativeto the total number of carbons in said wax,

-   -   and;    -   said wax is further characterized by having a set of endotherms        as determined by differential scanning calorimetry (DSC) run at        a rate of 10° C. per minute, said endotherms characterized by a        primary endotherm and at least a secondary endotherm, said        primary endotherm exhibiting a temperature range of between        70° C. and 90° C., and said secondary endotherm exhibiting a        temperature range of between 95° C. and 110° C.,    -   and;    -   wherein said wax has a crystallinity of from 75% to 90% as        determined by X-ray diffraction analysis.    -   and;        wherein said wax is also characterized by having a molecular        weight polydispersity (Mw/Mn) in the range of 1.1-1.3, where the        number average molecular weight is in the range of 700-790 and        the weight average molecular weight is in the range of 890-1000.        Toner Components

The toner in the present invention can be prepared by any of thegenerally known methods in the art and various known toner constituentingredients can be used.

Binder resins for the toner can be selected from a wide variety ofmaterials including known thermoplastic resins. There can be mentioned,for example, styrene resin (homo- or copolymer containing styrene orsubstituted styrene) such as a polystyrene, polychlorostyrene,poly-methylstyrene, styrene-chlorostyrene polymer, styrene-propylenecopolymer, styrene-butadiene copolymer, styrene-vinyl chloridecopolymer, styrene-vinyl acetate copolymer, styrene-maleic acidcopolymer, styrene-acrylate copolymer (for example, styrene-methylacrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butylacrylate copolymer, styrene-octyl acrylate copolymer and styrene-phenylacrylate copolymer), styrene-methacrylate copolymer (for example,styrene-methyl methacrylate copolymer, styrene-ethyl methacrylatecopolymer, styrene-butyl methacrylate copolymer and stryene-phenylmethacrylate copolymer), styrene-methyl α-chloroacrylate copolymer andstyrene-acrylonitrile-acrylate copolymer, vinyl chloride resin, resinmodified maleic acid resin, phenolic resin, epoxy resin, saturated orunsaturated polyester resin, low molecular weight polyethylene, lowmolecular weight polypropylene, ionomer resin, polyurethane resin,silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xyleneresin and polyvinyl butyral resin. Preferred resins include styreneresins, and saturated or unsaturated polyester resins. Further, theabove-mentioned resins may be used not only alone, but also as acombination of two or more of them.

Resins typically exhibit a softening temperature and a flow temperature.As used herein “softening temperature” is intended to refer to thetemperature at which particle collapse begins, and “flow temperature” isintended to refer to the temperature at which the resin achievessufficient liquidity to be extruded in a capillary rheometer. Thesoftening temperature can be determined using rheometers such as theSHIMADZU® capillary rheometer.

The resins for use in toner particulate may include a crosslinking agentin an amount of from about 0.01 to about 5 parts by weight per 100 partsby weight of the monomers employed therein. Conventional crosslinkingagents may be used. In one embodiment, the toner comprises a resin whichis free of crosslinking agents.

Toner particles may comprise more than one resin. Generally, the resinswill have a glass transition temperature of no less than 50° C. In oneembodiment the particulate comprises a first resin and a second resin,each resin having a glass transition temperature of no less than about50° C., preferably no less than about 55° C. Generally the resins willhave molecular weight greater than about 2000.

In order to use the toner of the present invention in the form of amagnetic toner, magnetic powder generally known in the art may also beincorporated therein. The magnetic powder for the toner of the presentinvention is preferably chosen from the ferromagnetic materialsexhibiting ferromagnetism including ferrimagnetism in a workingcircumstance temperature (around 0 to 60° C.) for office businessmachines, plain paper copiers, printers, etc. For example, there can bementioned magnetic powder showing ferromagnetism or ferrimagnetism in atemperature range of about 0 to 60° C., selected from magnetite (Fe₃O₄),maghemite (—Fe₂O₃), a complex of magnetite and maghemite, spinal ferritesuch as ferrite (M_(x)Fe_(3-x)O₄ in which M represents Mn, Fe, Co, Ni,Cu, Mg, Zn, Cd or mixed crystal materials thereof), hexagonal ferritessuch as BaO.6Fe₂O₃, garnet-type oxide such as Y₃ Fe₅O₁₂, retile-typeoxide such as CrO₂, metal such as Fe, Mn, Ni, Co, and Cr, as well asother ferromagnetic alloys. Among them, a powder of magnetite, maghemiteor a complex product of magnetite and maghemite with an average particlesize of not more than 3 μm, about 0.01 to 1 μm are preferred in view ofthe performance and the cost. The above-mentioned magnetic powder may beused not only alone but also as a combination of two or more of them.

As an example of manufacture of mono-component magnetic toner, theblending weight ratio of the binder resin to the magnetic powder can beselected within a range from 1:3 to 7:1, while taking the fixingproperty to a transfer material into consideration.

As a colorant used for the toner, any of known dyes and pigments such ascarbon black, lamp black, ultramarine, nigrosine dye, aniline blue,phthalocyanine blue, phthalocyanine green, hanza yellow G, rhodaminetype dye and pigment, chrome yellow, quinacridone, benzidine yellow,rose bengale, triallylmethane dyes, monoazo and disazo dyes and pigmentsmay be used alone or in admixture. The addition amount of the colorantinto the toner is preferably from 0.1 to 30 parts by weight, morepreferably 0.5 to 10 parts by weight, based on 100 parts by weight ofthe binder resin. The fixing properties become poor if the amount isexcessive, thus showing tendencies in property performance that isundesirable.

The charging property of the toner in the present invention may becontrolled by the binder resin or the dye and pigment per se and, ifrequired, a charge control agent causing no problem in view of colorreproduction may also be used together. It is also possible to includecharge control resins.

Examples of the charge controller are well known by way of reference forexample, U.S. Pat. No. 4,957,840, incorporated herein by reference. Forpositive charge control agents, examples may include: nigrosine and itsmodification products modified by a fatty acid metal salt; quaternaryammonium salts, such as tributylbenzyl-ammonium-1hydroxy-4-naphthosulfonic acid salt, and tetrabutylammoniumtetrafluoroborate; diorganotin oxides, such as dibutyltin oxide,dioctyltin oxide, and dicyclohexyltin oxide; and diorganotin borates,such as dibutyltin borate, dioctyltin borate, and dicyclo-hexyltinborate; and triphenylmethane compound. These positive charge controllersmay be used singularly or as a mixture of two or more species. Asanother type of positive charge controller, there may be use of ahomopolymer of a monomer having an amino group represented by theformula:

wherein R₁ represents H or CH₃;and R₂ and R₃ each represent a substituted or unsubstituted alkyl group(preferably C₁-C₄); or a copolymer of the monomer having an amine groupwith another polymerizable monomer such as styrene, acrylates, andmethacrylates as described above. In this case, the positive chargecontroller may also function as a binder.

Examples of negative charge control agents include: metal complexes orsalts of monoazo dyes, salicylic acid, alkylsalicylic acid,dialkylsalicylic acid, naphthonic acid, or acetylacetone. It ispreferred that the above-mentioned charge controller is used in the formof fine powder. In such a case, the number-average particle size thereofmay preferably be 4 microns or smaller, more preferably 3 microns orsmaller.

In the case of internal addition, such charge controller may preferablybe used in an amount of 0.1-20 wt. parts, more preferably 0.2-10 wt.parts, per 100 wt. parts of a binder resin by taking into considerationthe conditions for the manufacturing method including the chargeabilityof the binder resin, the addition amount of the colorant and thedispersion method, as well as the chargeability of the other additives.

The toner in the present invention may preferably have a volume medianparticle size from 4 to 20 μm, more preferably from 5 to 15 μm, and mostpreferably from 6 to 12 μm, where the volume median particle size isobtained by using a Coulter counter Model Multisizer with a 100 micronaperture.

The toner of the present invention may contain one or more of thefollowing external ingredients in small amounts, preferably 5% or less,more preferably 2% or less, still more preferably 1% or less, based ontotal amount of toner: straight chain saturated fatty acids such aspalmitic acid, stearic acid and montanic acid; unsaturated fatty acidssuch as brassidic acid, eleostearic acid and parinnaric acid; saturatedalcohols such as stearyl alcohol aralkyl alcohol, behenyl alcohol,carnaubyl alcohol, ceryl alcohol and melissyl alcohol; polyhydricalcohols such as sorbitol; fatty acid amides such as linolic acid amide,oleic acid amide, and lauric acid amide; saturated fatty acid bisamidessuch as methylenebisstearic acid amide, ethylenebiscapric acid amide,ethylenebislauric acid amide, and hexamethylenebisstearic acid amide;unsaturated fatty amides such as ethylenebisoleic acid amide,hexamethylenebisoleic acid amide, N,N′-bis-dioleyladipic acid amide andN,N′-bis-dioleylsebacic acid amide; aromatic bisamides such asxylene-bis-stearic acid amide and N,N′-distearylisophthalic acid amide;fatty acid metal: salts (what are commonly called metal soaps) such ascalcium stearate, calcium laurate, zinc stearate, and magnesiumstearate; waxes obtained by grafting vinyl monomers such as styrene andacrylic acid onto aliphatic hydrocarbon waxes; partially esterifiedproducts of fatty acids such as behenic acid monoglyceride withpolyhydric alcohols; and methyl ester compounds having a hydroxyl group,obtained by hydrogenation of vegetable fats and oils.

Organic particles for charge control that are employed in the tonercompositions may be chosen separately from resinous materials. Examplesof such resinous materials are exemplified by, but not limited to,thermoplastic resins such as polystyrenes, poly(meth) acrylic resins,polyolefin resins, polyamide resins, polycarbonate resins, polyetherresins, poly (sulfine acid) resins, polyester resins, epoxy resins,polybutyral resins, urea resins, urethane/urea resins, silicon resins,polyethytlene resins, Teflon resins and the like (fluoropolymer resins),thermosetting resins, a mixture thereof, block copolymers thereof, graftcopolymers thereof, a blend thereof, and the like.

The inorganic oxide particles that are employed for toner compositionsmay also be prepared by any methods known in the art and are preferablyselected from the group consisting of SiO₂, Al₂O₃, W₂O₃, ZrO₂, SeO,TiO₂, ZnO and MgO. The particles preferably have a BET measurement valueof not less than 1 m²/g, more preferably not less than 30 m²/g and evenmore preferably not less than 100 m²/g.

The toner of the present invention can be used in conventionalelectrophotography processes using conventional toner cartridges. Suchelectrophotography processes and toner cartridges are well known in theart. Some have been described in various patents cited herein andincorporated by reference. Others are detailed in U.S. Pat. Nos.6,391,510 and 5,520,229, the relevant portions of which are herebyincorporated by reference.

Toner Wax

The toner used in the present invention contains the linear wax which isan uncrosslinked, linear hydrocarbon based homopolymer, wherein the waxhas a total number of branches present in each of one or more chainsthat is less than 0.5% relative to the total number of carbons in saidwax. The wax is further characterized by having a set of endotherms asdetermined by differential scanning calorimetry (DSC) It consists of theprimary endotherm and at least a secondary endotherm: the primaryendotherm exhibits a temperature range of between 70° C. and 90° C. andthe secondary endotherm exhibits a temperature range of between 95° C.and 110° C.

DSC test results were determined by running one heating followed by onecooling followed by one heating cycle each at 10° C. per minute, with aninitial heating and cooling cycle prior to the second heating duringwhich test measurements were made.

The wax further has a crystallinity of from 75% to 90% as determined byX-ray diffraction analysis.

X-ray diffraction analysis was performed in a URTRAX 18 (manufactured byRigaku) X-ray device utilizing a 40 kV-200 mA (8 kW) source. A samplewax powder was prepared for a cell 1 mm in thickness. The sample washeated to 130 C and held at that temperature for 5 minutes. Next, thesample was cooled to 60 C at 0.91 C/min and then left to continuecooling at ambient temperature for 2 hours.

The detection comprised;

-   -   A Cu Ka line monochromated by a graphite monochromater    -   A collimator 1 mm in diameter    -   A Slit of 0.5 mm×0.5 mm (height×width)    -   A detector scintillation counter and;    -   A step scan: 2 theta=10-20 degrees, at 0.1 deg/step, 20        seconds/step.

Crystallinity was calculated utilizing Igor Pro Software fromWavemetrics Corporation to separate and identify the peaks to crystalfaces.

The wax is also characterized by having a molecular weightpolydispersity (Mw/Mn) in the range of 1.1-1.3, with a number-averagemolecular weight in the range of 700-790 and a weight average molecularweight in the range of 890-1000.

Molecular Weight test results were determined by GPC analysis usingPL-210 instrument from Polymer Laboratories, using a 30 cm×4 column ofTSGgel GMH-HT (Toso) and ODCB (o-dichlorobenzene) as eluent, and arefractive index (RI) detector. The flow rate was 1.0 mL/min. The samplewas injected as a 0.1 wt % solution in the eluent and in an amount of500 μL. The column temperature was maintained at 135° C. The resultswere determined against a polystyrene standard with a cubic fitcalibration curve, along with a universal calibration curve with theviscosity equation of polystyrene standard and polyethylene ofKps=1.38E-4, α ps=0.70, Kpe=4.77E-4, α pe=0.70.

The wax of the present invention has branching that has been furthercharacterized by NMR as;

-   -   0-0.20 methyl branches per 100 carbon atoms,    -   0-0.10 ethyl branches per 100 carbon atoms and    -   0-0.10 butyl branches per 100 carbon atoms.

¹³C NMR spectrum was quantitatively analyzed to determine the numbers ofbranching carbons in the molecule. The NMR instrumentation included aVarian UnityPlus 400 with sample preparation utilizing the protoncomplete decoupling method as follows;

-   -   Resonance frequency: 100.56 MHz    -   Temperature: 130 C    -   Pulse Angle: 45 degrees    -   Pulse Interval: 20 seconds    -   Solvent: o-DCB/p-DCB d4

(DCB=dichlorobenzene, “d4” means that all of the four hydrogens weresubstituted with Deuterium)

The wax of the present invention preferably has a mean particle size offrom 1 to 10 μm, more preferably from 4-7 μm. The particle size for thewax has been determined by use of a Beckman Coulter Multisizer 3.33.

The wax of the present invention is also preferably prepared by aprocess comprising; gasifying and subsequent liquifying of coalresulting in residual wax residue forming in a reactor vessel, thereactor vessel containing sides with interior surfaces, wherein waxresidue forms specifically on the surfaces of the sides of the vessel,the vessel used for coal gasification and liquification followed bymilling of the wax, substantially by a jet mill to accomplishmicronizing and classifying of the linear hydrocarbon wax.

The wax is to provide an electrostatic developer comprising a toner ofthermal fixing type which is capable of providing a reprographic imagewhich exhibits good release properties upon thermal fixing, a reducedadhesion to the heated roller or the heated film, no offset orcontamination, and good fixing properties of the fixed image, and iscapable of preventing the heated roll or the heated film from undergoingcontamination.

Two test methods have been used to determine fusing strength for fusingproperties where fusing strength is descriptive of the bond strengthbetween the paper and the toner subsequent to the electrophotographicprocess. Once toner has been deposited on the paper and exposed to thefusing conditions, the toner has a fusing strength.

One test method, known as the “tape peeling test” includes the use of anadhesive tape, specifically Scotch 3M Magic Tape (¾ inch width). Theimage density (ID) is measured before and after the tape is applied andremoved.

The second test method, known as the “Rub Test Reference” uses the backside (non-adhesive side) of a Self-Stick Removable Notes Padmanufactured by either 3M or Highland. Non-adhesive paper side is placedover the fused toner image and is rubbed or moved from the top to thebottom of the paper (usually 2⅞″×2⅞″). After the “rub” is complete, thepaper is examined and a number is associated with the “smudge” if thereis one. The numbering system is as follows;

1: No smudge—acceptable

2: Very slight and no smear—acceptable

3: Slight: some smudging—marginal

4: Smear after rubbing is very apparent—unacceptable

5: Bad and lots of smear after rubbing—very unacceptable

It is permissible that the specific wax of the invention is used withone or more of those wax components such as polypropylene (PP) orpolyethylene (PE) as listed in U.S. Pat. No. 5,840,457 and/or with oneor more auxiliary agents such as various kinds of plasticizers andreleasing agents for adjusting thermal properties, physical properties,etc. The addition amount thereof is preferably from 0.1 to 20 parts byweight based on 100 parts by weight of the binder resin, and even morepreferably from 1-6 parts, by weight based on 100 parts by weight of thebinder resin.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples that are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified. These examples describe, but arenot limited to, the preparation of toner by conventional process meansas below.

EXAMPLES

In the following Examples and Comparative Examples, “parts by weight” ismerely written as “parts”.

Example 1

One hundred parts of a styrene-butyl acrylate copolymer (Mw=15.5×10⁴⁾,90 parts of magnetite, 4 parts of Wax-A, which was nearly linearhydrocarbon based homopolymer wax with a specific molecular weight(Mn=750 and Mw=966) and crystallinity (80.4%), and 1 part of a chromiumbased organic metal complex were all well blended and kneaded by meansof a twin screw extruder. The kneaded product was cooled, coarselycrushed by hammer mill, finally pulverized and classified to obtainblack particulate having a volume median particle size of 9.0 microns.

Then 100 parts of the above black particulate were mixed with 1 part ofTG308F (Cabot) negatively charged silica, which was fumed andpost-treated with polydimethylsiloxane (PDMS). The resultant mixture waspassed through a 100-mesh sieve.

Comparative example C1 was the same as Example 1 except for using PE130(Clariant) in place of Wax-A. Another comparative example C2 was thesame as Example 1 except for using NP505 (Mitsui Chemical) in place ofWax-A.

Those toner samples were subjected to print tests using a 50(prints/minute) speed laser printer machine. The approximate fusertemperature was 180 C. The fusing apparatus was visually inspected forcontamination.

Example 1 toner (Ex-1) showed good fusing properties as measured by tapepeeling and rubbing. The prints with Ex-1 had no fusing picker fingerscratches. The fusing unit was free from contamination after runningwith the Ex-1 toner.

TABLE 1 Working and Comparative Examples of Electrostatic Developer withVarying Amounts of Low Softening Temperature, Nearly Linear HydrocarbonBased Homopolymer Wax Wax Tape Rub Test Picker Sample (4 parts) ID TestReference Finger Contamination Ex-1 Wax-A 1.43 ◯ ◯ ◯ No contaminationC.1 PE130 1.33 X ◯ Δ No contamination C.2 NP505 1.32 X X X Contamination*1: Evaluation was carried out under normal temperature and humidity(N,N = 20-25 degree C., 40-70% RH) conditions. *2: ID was measured by aMacbeth RD914 Colorimeter *3: Tape test was conducted using Highlandtape and observed resultant image smudging *4: Paper rubbing wasconducted by using Post-It^(R) and observed resultant image smudging *5:Picker finger soil was observed on black page print. *6: Contaminationof fusing apparatus was observed after 30,000 pages.

The toner samples were tested using several different fusing conditions,changing fusing temperature and fusing speed to confirm thenon-offsetting range. Unfused prints using the toner samples were takenfrom a modified laser printer (HP LaserJet4Plus). The fusing apparatuswas a modified fusing unit of HP LaserJet5Si for this fusing test. Thistest indicated Ex-1 toner had a wider non-offsetting fusing range thanC1 or C2.

TABLE 2 Offsetting Performance for Example Toners Under Various FusingConditions Fusing mm/s 78 70 62 50 42 42 42 42 42 42 42 42 34 25 17 8Speed Fuser Temp. Deg. C. 130 130 130 130 130 140 150 160 170 180 190200 200 200 200 200 Example No. Ex. 1 4 3 2 2 1 1 1 1 1 1 1 1 1 1 1Comparative C-1 5 3 2 2 2 1 1 1 1 1 1 1 1 1 1 4 Example No. ComparativeC-2 5 5 3 3 2 3 3 2 2 2 2 1 1 1 1 1 Example No. 1: No offsetting -acceptable 2: Very slight offsetting - acceptable 3: Slight: someoffsetting - marginal 4: Offsetting is very apparent - unacceptable 5:Severe offsetting - very unacceptable

For characterization and evaluation of Wax-A;

DSC indicated that Wax-A had the primary endotherm at 82-83 C and thesecondary endotherm at 104 C.

DSC test results were determined by running one heating followed by onecooling followed by one heating cycle each at 10° C. per minute, with aninitial heating and cooling cycle prior to the second heating duringwhich test measurements were made. FIG. 1 represents a sample DSCmeasurement for Wax-A.

Wax-A was further characterized by ¹³C-NMR as;

-   -   0.13 methyl branches per 100 carbon atoms,    -   0.05 ethyl branches per 100 carbon atoms and    -   0.05 butyl branches per 100 carbon atoms.

¹³C NMR spectrum was quantitatively analyzed to determine the numbers ofbranching carbons in the molecule. The NMR instrumentation included aVarian UnityPlus 400 with sample preparation utilizing the protoncomplete decoupling method as follows having;

a resonance frequency: 100.56 MHz

a temperature: 130 C

a pulse angle: 45 degrees

a pulse interval: 20 seconds

and the solvent: o-DCB/p-DCB d4

(DCB=dichlorobenzene, “d4” means that all of the four hydrogens weresubstituted with Deuterium)

Wax-A had a crystallinity of 80.4-80.6% as determined by X-raydiffraction analysis.

Crystallinity test results were determined by X-ray diffraction analysiswas performed in a URTRAX 18 (manufactured by Rigaku) X-ray deviceutilizing a 40 kV-200 mA (8 kW) source. A sample wax powder was preparedfor a cell 1 mm in thickness. The sample was heated to 130 C and held atthat temperature for 5 minutes. Next, the sample was cooled to 60 C at0.91 C/min and then left to continue cooling at ambient temperature for2 hours.

The detection comprised;

a Cu Ka line monochromated by a graphite monochromater

a collimator 1 mm in diameter

a Slit of 0.5 mm×0.5 mm (height×width)

a detector scintillation counter and;

a step scan: 2 theta=10-20 degrees, at 0.1 deg/step, 20 seconds/step.

Crystallinity was calculated utilizing Igor Pro Software fromWavemetrics Corporation to separate and identify the peaks to crystalfaces.

Wax-A was also characterized by having a molecular weight polydispersity(Mw/Mn) of 1.3, with the number average molecular weight Mn of 750 andthe weight average molecular weight Mw of 965.

Molecular Weight test results were determined by GPC analysis usingPL-210 instrument from Polymer Laboratories, using a 30 cm×4 column ofTSGgel GMH-HT (Toso) and ODCB (o-dichlorobenzene) as eluent, and arefractive index (RI) detector. The flow rate was 1.0 mL/min. The samplewas injected as a 0.1 wt % solution in the eluent and in an amount of500 μL. The column temperature was maintained at 135° C. The resultswere determined against a polystyrene standard with a cubic fitcalibration curve, along with a universal calibration curve with theviscosity equation of polystyrene standard and polyethylene ofKps=1.38E-4, α ps=0.70, Kpe=4.77E-4, α pe=0.70.

The sample was prepared by dissolving the wax in ODCB with heating at135° C. in an oil bath, followed by filtering the hot solution with a 3um PTFE filter. FIG. 2 illustrates the drastic differences in molecularweight distributions between PE 130 and Wax-A.

The composition of the present invention (containing Wax-A) showedsignificantly higher ID than any of the other formulations tested, whichonly differed in the type of wax that was used.

This application is based on U.S. provisional application Ser. No.60/408,878, filed Sep. 9, 2002, the entire contents of which are herebyincorporated by reference.

Obviously, additional modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. An electrostatic developer, comprising: toner-containingimage-forming particles and an uncrosslinked, linear hydrocarbon basedhomopolymer wax, wherein said wax has a total number of branches in eachof one or more chains that is less than 0.5%, relative to a total numberof carbons in said wax, wherein said wax has a set of endotherm peaks asdetermined by differential scanning calorimetry (DSC) run at a maximumrate of 10° C. per minute at increasing temperature, said endothermpeaks including a primary endotherm peak and at least a secondaryendotherm peak, said primary endotherm peak in a temperature range ofbetween 70° C. and 90° C. and said secondary endotherm peak in atemperature range of between 95° C. and 110° C.; wherein said wax has acrystallinity of from 78 to 82% as determined by small angle X-raydiffraction analysis; wherein said wax has a molecular weightpolydispersity (Mw/Mn) in the range of 1.1-1.3, wherein the numberaverage molecular weight, Mn, is in the range of 700-790 and the weightaverage molecular weight, Mw, is in the range of 890-1000; and whereinsaid wax has the following branching: 0-0.20 methyl branches per 100carbon atoms, 0-0.10 ethyl branches per 100 carbon atoms and 0-0.10butyl branches per 100 carbon atoms.
 2. The electrostatic developer ofclaim 1, wherein said wax is further characterized by a particle size inthe range of 1 to 10 μm.
 3. The electrostatic developer of claim 1,wherein said wax is obtained by a process comprising: in a reactorvessel, gasifying and subsequently liquifying coal to produce a waxresidue in the reactor vessel, said reactor vessel containing sides withinterior surfaces, wherein the wax residue forms on said surfaces;milling said wax residue, substantially by a jet mill to accomplishmicronizing of the wax.
 4. The electrostatic developer of claim 1,wherein said toner is a monocomponent toner.
 5. The electrostaticdeveloper of claim 1, wherein said toner is a dual component toner. 6.The electrostatic developer of claim 5, wherein said toner furthercomprises magnetic particles.
 7. The electrostatic developer of claim 1,wherein said toner further comprises a binder resin.
 8. Theelectrostatic developer of claim 1, wherein said toner further comprisesa binder resin, and wherein said wax is present in an amount of 0.1-20parts by weight per 100 parts of the binder resin.
 9. The electrostaticdeveloper of claim 1, said toner further comprises a binder resin, andwherein said wax is present in an amount of 0.1-7.0 parts by weight per100 parts of binder resin.
 10. The electrostatic developer of claim 1,said toner further comprises a binder resin, and wherein said wax ispresent in an amount of 1.0-6.0 parts by weight per 100 parts of binderresin.
 11. The electrostatic developer of claim 1, further comprisingone or more inorganic oxides selected from the group consisting of SiO₂,Al₂O₃, W₂O₃, ZrO₂, SeO, TiO₂, ZnO, MgO, and mixtures thereof.
 12. Atoner cartridge comprising a cartridge and the electrostatic developeraccording to claim
 1. 13. In an electrophotographic apparatus, whereinthe improvement comprises the use of a toner cartridge according toclaim
 12. 14. An electrostatic developer, comprising: toner-containingimage-forming particles and an uncrosslinked, linear hydrocarbon basedhomopolymer wax; wherein said wax has a total number of branches in eachof one or more chains that is less than 0.5%, relative to a total numberof carbons in said wax; wherein said wax has a set of endotherm peaks asdetermined by differential scanning calorimetry (DSC) run at a maximumrate of 10° C. per minute at increasing temperature, said endothermpeaks including a primary endotherm peak and at least a secondaryendotherm peak, said primary endotherm peak in a temperature range ofbetween 70° C. and 90° C. and said secondary endotherm peak in atemperature range of between 95° C. and 110° C.; and wherein said waxhas a crystallinity of from 75 to 90% as determined by small angle X-raydiffraction analysis.
 15. The electrostatic developer of claim 14,wherein said wax has a molecular weight polydispersity (Mw/Mn) in therange of 1.1-1.3, wherein the number average molecular weight, Mn, is inthe range of 700-790 and the weight average molecular weight, Mw, is inthe range of 890-1000; and wherein said wax has the followingbranching: >0 to 0.20 methyl branches per 100 carbon atoms, >0 to 0.10ethyl branches per 100 carbon atoms, and >0 to 0.10 butyl branches per100 carbon atoms.